A knife is well-known from published prior use. It comprises a housing in which a blade holder is located. The blade holder can be moved between a safety position and a cutting position. The blade is inaccessible in the housing when in the safety position, and projects from the housing when in the cutting position. A spring is fastened to the housing and to the blade holder, and urges the blade holder for example into the safety position.
The blade holder is often removed from the housing in order to change blades. As this is done, the spring is frequently overstretched and thus destroyed.